Frequency crossover

I got my Oticon Gaia yesterday. I tried it yesterday. I found the speech was not clear. My dispenser adjusted the frequency crossover towards lower frequency. Now it is about 800K. The speech is more natural and clear. I wonder should I ask my dispenser to even lower the crossover frequency towards the lowest frequency. Anyone has any suggestion?
Besides the crossover frequency, anything can enhance the speech intelligency? High frequency gain? lower compression ratio?